RESUMO
PURPOSE: Evaluate 21 formulation vehicles administered to rabbits after intravitreal injection for tolerability and safety. METHODS: Forty-two Dutch Belted rabbits were anesthetized, and the eyes received a single intravitreal injection of the excipient formulation. Clinical signs and ocular irritation responses were recorded twice daily for 7 days and microscopic evaluation of the eyes, optic nerve, and eyelids was completed at 1-week post treatment. RESULTS: Saline (≥ 300 mOsm and ≤ 592 mOsm at pH 7.0 or 300 mOsm at pH 8.0) and 10 formulation excipients; (10% w/v PEG 3350 at pH 7.4, 1% polysorbate 21 at pH 7.4, PVA at pH 7.0, 0.2% polysorbate 80 at pH 7.2, 0.2% Pluronic F108® at pH 7.3, 2%, 100 mM sodium sulfate at pH 3.2, 2 mM sodium glycocholate at pH 7.4, and 275 mM D-mannitol pH 7.0 in sterile water, and 100 mM sodium phosphate in combination with 0.9% NaCl 300 mOsm and 0.01% or 0.05% polysorbate 80 at pH 7.4) considered as formulation vehicles for intravitreal injectables, were well-tolerated in rabbits. Clinical signs were transient and microscopic changes were not observed. CONCLUSIONS: Of the 21 formulation vehicles evaluated, 10 formulation vehicles were well-tolerated in rabbits and feasible candidates for future investigations.
Assuntos
Excipientes/administração & dosagem , Excipientes/efeitos adversos , Segmento Posterior do Olho/efeitos dos fármacos , Animais , Composição de Medicamentos , Injeções Intravítreas , Segmento Posterior do Olho/patologia , Segmento Posterior do Olho/ultraestrutura , Coelhos , Solução Salina/administração & dosagem , Solução Salina/efeitos adversosRESUMO
Retinal toxicity is one of the leading causes of attrition in drug development, and drug-induced retinal toxicity remains an issue in both drug discovery and postmarketed drugs. Derisking strategies to help with early identification of retinal injury utilizing a predictive retinal miRNA biomarker would greatly benefit decision-making in drug discovery programs, ultimately reducing attrition due to retinal toxicity. Our previous work demonstrated elevation of circulating retina-enriched miRNAs in a retinal toxicity model. To further validate our previous observation, 2 additional rat retinal injury models were utilized in this study: NaIO3-induced retinal injury and laser-induced choroidal neovascularization (CNV) injury model. Following induction of retina tissue injuries, circulating miR-183/96/182 cluster (miR-183 cluster), and miR-124 was investigated, as well as evaluations using an electroretinogram (ERG) and histopathology analysis. Data revealed that circulating miR-183/96/182 cluster was significantly increased (2- to 15-fold) compared with baseline/control in both laser-induced CNV and NaIO3-induced retinal injury models. Moreover, the severity of the retinal injury evaluated by ERG and histopathology correlated highly with elevation of these retina-enriched miRNAs in plasma. MiR-124 was also significantly increased in comparison with baseline/control by â¼25-fold postrepeat-doses of 30 mg/kg NaIO3 treatment. Increased level of these plasma miRNA biomarkers appeared to be dose- and time-dependent upon NaIO3 or laser treatment. The results suggest that the retina-enriched miRNAs (miR-183/96/182 cluster and miR-124) could serve as convenient and predictive biomarkers of retinal toxicity in drug development.
Assuntos
Biomarcadores/sangue , MicroRNAs/sangue , Retina/efeitos dos fármacos , Testes de Toxicidade , Animais , Eletrorretinografia , Feminino , Masculino , Ratos , Ratos Wistar , Retina/fisiopatologiaRESUMO
Retinal ocular toxicity is among the leading causes of drug development attrition in the pharmaceutical industry. Electroretinography (ERG) is a non-invasive functional assay used to assess neuro-retinal physiological integrity by measuring the electrical responses. To directly assess the utility of ERG, a series of studies was conducted following intravitreal and/or iv administration of pan-cyclin-dependent kinase inhibitors: AG-012,986 and AG-024,322 in rats. Both compounds have previously shown to induce retinal toxicity. Retinal injury was evaluated by ERG, histopathology and TUNEL staining. Intravitreal injection of AG-012,986 at ≥ 10 µg/eye resulted in decreases (60%) in ERG b-wave and microscopic changes of mild to moderate retinal degeneration, and at 30 µg/eye led to additional ophthalmic findings. Intravenous administration of AG-012,986 daily at ≥ 5 mg/kg resulted in dose-related decreases (25 to 40%) in b-wave and sporadic to intense positive TUNEL staining. Intravitreal injection of AG-024,322 at 30 µg/eye also resulted in decreases (50 to 60%) in b-wave, mild to marked retinal degeneration and mild vitreous debris. These experiments demonstrate that ERG can be used as a sensitive and reliable functional tool to evaluate retinal toxicity induced by test compounds in rats complementing other classical ocular safety measurements.
Assuntos
Benzamidas/efeitos adversos , Benzimidazóis/efeitos adversos , Quinases Ciclina-Dependentes/antagonistas & inibidores , Indazóis/efeitos adversos , Retina/efeitos dos fármacos , Retina/patologia , Tiazóis/efeitos adversos , Animais , Benzamidas/administração & dosagem , Benzimidazóis/administração & dosagem , Quinases Ciclina-Dependentes/metabolismo , Descoberta de Drogas/métodos , Eletrorretinografia/métodos , Marcação In Situ das Extremidades Cortadas/métodos , Indazóis/administração & dosagem , Injeções Intravítreas/métodos , Masculino , Ratos , Degeneração Retiniana/patologia , Tiazóis/administração & dosagemRESUMO
This investigation examined microRNA-208a (miR-208a) as a potential biomarker of isoproterenol (ISO)-induced cardiac injury in superoxide dismutase-2 (Sod2(+/-) ) and the wild-type mice, and the potential sensitivity of Sod2(+/-) mice to ISO-induced toxicity. A single intraperitoneal injection of ISO was administered to age-matched wild-type and Sod2(+/-) mice at 0, 80, or 160 mg/kg. Plasma miR-208a, cardiac troponin I (cTnI), and ISO systemic exposure were measured at various time points postdose. Hearts were collected for histopathology examination and for tissue expression of miR-208a and myosin heavy chain 7. ISO administration caused increases in cTnI and miR-208a plasma levels that correlated with myocardial damage; however, the magnitude of increase differed according to the types of mice. At similar ISO systemic exposure, the magnitude of cTnI was greater in wild-type mice compared to Sod2(+/) (-) mice; however, the magnitude of miR-208a was greater in Sod2(+/-) mice than that of the wild-type mice. Myocardial degeneration occurred at ≥3 hr in the wild-type and ≥6 hr in Sod2(+/) (-) mice. At ≥24 hr after ISO administration, miR-208a appeared superior to cTnI in indicating myocardial injury in both wild-type and Sod2(+/-) mice. Sod2(+/-) mice were not more sensitive than wild-type mice to ISO-induced toxicity.
Assuntos
Biomarcadores/sangue , Coração/efeitos dos fármacos , Isoproterenol/toxicidade , MicroRNAs/sangue , Animais , Miosinas Cardíacas/sangue , Cardiomiopatias/induzido quimicamente , Cardiomiopatias/patologia , Caspase 3/metabolismo , Feminino , Coração/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Cadeias Pesadas de Miosina/sangue , Superóxido Dismutase/metabolismo , Troponina I/sangueRESUMO
Dexamethasone was given in 2 oral dosing regimens with repeat dose oral administration of the gamma secretase inhibitor (GSI), PF-03084014, in Sprague-Dawley (SD) rats in order to evaluate the effects of coadministration of dexamethasone on GSI-induced goblet cell hyperplasia (GCH) in the intestinal tract. Safety end points were evaluated in 1 week and 1 month studies. The dosing regimens tested in the 1-month studies included a 1-week pretreatment with 1.0 mg/kg dexamethasone followed by a 3-week repeat dose treatment with 100 mg/kg GSI or concurrent intermittent treatment with 1.0 mg/kg dexamethasone on weeks 1 and 3 and repeat dose treatment with 100 mg/kg GSI for 4 weeks. Pretreatment with dexamethasone for 1 week transiently mitigated the severity of intestinal GCH for up to 1 week. Intermittent coadministration of dexamethasone on weeks 1 and 3 with GSI repeat dosing for 4 weeks mitigated intestinal GCH for up to 4 weeks post treatment. Treatment-related morbidity and mortality occurred on day 7 with 150 mg/kg GSI and 5 mg/kg dexamethasone coadministration, and on days 13, 14, and 23 with 100 mg/kg GSI and 1 mg/kg dexamethasone coadministration.
Assuntos
Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Dexametasona/administração & dosagem , Células Caliciformes/efeitos dos fármacos , Hiperplasia/patologia , Tetra-Hidronaftalenos/administração & dosagem , Valina/análogos & derivados , Administração Oral , Animais , Peso Corporal/efeitos dos fármacos , Dexametasona/sangue , Dexametasona/toxicidade , Células Caliciformes/citologia , Células Caliciformes/metabolismo , Intestinos/citologia , Intestinos/efeitos dos fármacos , Masculino , Ratos , Ratos Sprague-Dawley , Tetra-Hidronaftalenos/sangue , Tetra-Hidronaftalenos/toxicidade , Valina/administração & dosagem , Valina/sangue , Valina/toxicidadeRESUMO
The hepatocyte growth factor (HGF)/c-Met signaling axis is deregulated in many cancers and plays important roles in tumor invasive growth and metastasis. An exclusively selective c-Met inhibitor (S)-6-(1-(6-(1-methyl-1H-pyrazol-4-yl)-[1,2,4]triazolo[4,3-b]pyridazin-3-yl)ethyl)quinoline (8) was discovered from a highly selective high-throughput screening hit via structure-based drug design and medicinal chemistry lead optimization. Compound 8 had many attractive properties meriting preclinical evaluation. Broad off-target screens identified 8 as a pan-phosphodiesterase (PDE) family inhibitor, which was implicated in a sustained increase in heart rate, increased cardiac output, and decreased contractility indices, as well as myocardial degeneration in in vivo safety evaluations in rats. Compound 8 was terminated as a preclinical candidate because of a narrow therapeutic window in cardio-related safety. The learning from multiparameter lead optimization and strategies to avoid the toxicity attrition at the late stage of drug discovery are discussed.
Assuntos
Cardiomiopatias/enzimologia , Inibidores de Fosfodiesterase/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Quinolinas/farmacologia , Receptores Proteína Tirosina Quinases/antagonistas & inibidores , Animais , Feminino , Humanos , Camundongos , Camundongos Nus , Modelos Moleculares , Inibidores de Fosfodiesterase/química , Inibidores de Proteínas Quinases/química , Quinolinas/química , Ratos , Receptores Proteína Tirosina Quinases/químicaRESUMO
PF-04254644 is a selective kinase inhibitor of mesenchymal epithelial transition factor/hepatocyte growth factor receptor with known off-target inhibitory activity against the phosphodiesterase (PDE) family. Rats given repeated oral doses of PF-04254644 developed a mild to moderate myocardial degeneration accompanied by sustained increase in heart rate and contractility. Investigative studies were conducted to delineate the mechanisms of toxicity. Microarray analysis of Sprague-Dawley rat hearts in a 6 day repeat dose study with PF-04254644 or milrinone, a selective PDE3 inhibitor, revealed similar perturbation of the cyclic adenosine monophosphate (c-AMP) pathway. PDE inhibition and activation of c-AMP were further substantiated using PDE3B immunofluorescence staining and through a c-AMP response element reporter gene assay. The intracellular calcium and oxidative stress signaling pathways were more perturbed by treatment with PF-04254644 than milrinone. The rat cardiomyocytes calcium assay found a dose-dependent increase in intracellular calcium with PF-04254644 treatment. These data suggest that cardiotoxicity of PF-04254644 was probably due to activation of c-AMP signaling, and possibly subsequent disruption of intracellular calcium and oxidative stress signaling pathways. The greater response with PF-04254644 as compared with milrinone in gene expression and micro- and ultrastructural changes is probably due to the broader panel of PDEs inhibition.
Assuntos
Miocárdio/enzimologia , Miocárdio/ultraestrutura , Miócitos Cardíacos/efeitos dos fármacos , Inibidores de Fosfodiesterase/efeitos adversos , Inibidores de Proteínas Quinases/efeitos adversos , Quinolinas/efeitos adversos , Animais , Cálcio/metabolismo , Células Cultivadas , AMP Cíclico/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/genética , Relação Dose-Resposta a Droga , Expressão Gênica/efeitos dos fármacos , Genes Reporter , Masculino , Milrinona/farmacologia , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/ultraestrutura , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
The c-MET receptor tyrosine kinase is an attractive oncology target because of its critical role in human oncogenesis and tumor progression. An oxindole hydrazide hit 6 was identified during a c-MET HTS campaign and subsequently demonstrated to have an unusual degree of selectivity against a broad array of other kinases. The cocrystal structure of the related oxindole hydrazide c-MET inhibitor 10 with a nonphosphorylated c-MET kinase domain revealed a unique binding mode associated with the exquisite selectivity profile. The chemically labile oxindole hydrazide scaffold was replaced with a chemically and metabolically stable triazolopyrazine scaffold using structure based drug design. Medicinal chemistry lead optimization produced 2-(4-(1-(quinolin-6-ylmethyl)-1H-[1,2,3]triazolo[4,5-b]pyrazin-6-yl)-1H-pyrazol-1-yl)ethanol (2, PF-04217903), an extremely potent and exquisitely selective c-MET inhibitor. 2 demonstrated effective tumor growth inhibition in c-MET dependent tumor models with good oral PK properties and an acceptable safety profile in preclinical studies. 2 progressed to clinical evaluation in a Phase I oncology setting.
Assuntos
Antineoplásicos/farmacologia , Descoberta de Drogas , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-met/antagonistas & inibidores , Pirazinas/farmacologia , Triazóis/farmacologia , Sequência de Aminoácidos , Animais , Antineoplásicos/química , Antineoplásicos/metabolismo , Linhagem Celular Tumoral , Estabilidade de Medicamentos , Ensaios de Triagem em Larga Escala , Humanos , Indóis/química , Modelos Moleculares , Dados de Sequência Molecular , Oxindóis , Conformação Proteica , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/metabolismo , Proteínas Proto-Oncogênicas c-met/química , Proteínas Proto-Oncogênicas c-met/metabolismo , Pirazinas/química , Pirazinas/metabolismo , Especificidade por Substrato , Triazóis/química , Triazóis/metabolismoRESUMO
Maleic acid was formulated in 0.7% saline and injected intravitreally in rabbits in order to evaluate ocular safety and tolerability. Maleic acid was formulated within a narrow pH range (2-3), administered in a fixed volume (100 µl), and concentrations ranged from 0.00 to 2.00 mg/eye (0.00 to 12.30 mM vitreous). Ocular evaluations were conducted at 2, 4, and 8 days post injection. Ocular irritation responses were observed at doses from 0.50 mg/eye (3.07 mM vitreous) to 2.00 mg/eye (12.30 mM vitreous) and included conjunctival redness and scleral swelling. Chemosis was observed at 2.00 mg/eye (12.30 mM vitreous). Funduscopic evaluations revealed enlarged retinal blood vessels and optic disk swelling at doses ≥1.50 mg/eye (9.22 mM vitreous), retinal folds and retinal discoloration at 2.00 mg/eye (12.30 mM vitreous). Histopathologic evaluations on days 4 and 8 post injection revealed retinal degeneration at doses ≥1.0 mg/eye (6.15 mM vitreous), conjunctival inflammation at doses ≥1.5 mg/eye (9.22 mM vitreous), and retinal pigment epithelial hypertrophy, optic nerve demyelination, anterior chamber fluid, and conjunctival fibrosis at 2.00 mg/eye (12.30 mM vitreous) maleic acid. The data suggest that maleic acid formulations at ≥1.00 mg/eye (6.15 mM vitreous) were not suitable for intraocular indications.
Assuntos
Excipientes/toxicidade , Injeções Intravítreas/métodos , Maleatos/toxicidade , Doenças Retinianas/fisiopatologia , Visão Ocular/efeitos dos fármacos , Animais , Câmara Anterior/efeitos dos fármacos , Câmara Anterior/fisiopatologia , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Excipientes/administração & dosagem , Olho/efeitos dos fármacos , Olho/fisiopatologia , Feminino , Pressão Intraocular/efeitos dos fármacos , Maleatos/administração & dosagem , Oftalmoscopia/métodos , Coelhos , Retina/efeitos dos fármacos , Retina/fisiopatologia , Doenças Retinianas/induzido quimicamente , Medição de RiscoRESUMO
The receptor tyrosine kinase receptor (RTK) signaling pathway, mesenchymal-epithelial transition factor (c-Met)/hepatocyte growth factor receptor (HGFR), has been implicated in oncogenesis and is a target of interest in cancer therapy. PF-04254644 is a potent and selective inhibitor of c-Met/HGFR. Wide ligand binding profiling of PF-04254644 revealed a potentially significant interaction with phosphodiesterase (PDE) 3, and follow-up PDE enzyme activity assays confirmed PF-04254644 as a potent inhibitor of PDE3 as well as other PDEs (1, 2, 5, 10, and 11). Clinical observations, laboratory, and echocardiography parameters were recorded in Sprague-Dawley (SD) rats that received PF-04254644 oral dosing for up to seven consecutive days. Toxicological evaluations revealed myocardial degeneration as an adverse event at all tested doses. Echocardiographic evaluations revealed an increase in heart rate (HR) and contractility after the first dose with PF-04254644 and myocardial fibrosis correlated with decreased cardiac function after repeat dosing. A study in telemetry-instrumented rats substantiated that PF-04254644 induced a sustained increased HR and decreased contractility after six days of treatment. Data suggest that the decreased cardiac function and cardiotoxicity are likely due to inhibition of multiple PDEs by PF-04254644.
Assuntos
Coração/efeitos dos fármacos , Miocárdio/patologia , Diester Fosfórico Hidrolases/efeitos dos fármacos , Inibidores de Proteínas Quinases/toxicidade , Quinolinas/toxicidade , Animais , Frequência Cardíaca/efeitos dos fármacos , Masculino , Contração Miocárdica/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
Prostaglandin receptor agonists have intraocular pressure-lowering effects in humans and are of interest in the treatment of glaucoma. The prostanoid receptor agonist PF-04475270 is a potent and selective agonist of the prostaglandin E(2) receptor EP4. This paper characterizes the toxicity associated with topical ocular administration of PF-04475270 in beagles. Dogs were given PF-04475270 topically to the eye on a consecutive daily dosing schedule for one or four weeks followed by a one-or four-week reversal period, respectively. Clinical observations, ophthalmic, and laboratory parameters were recorded. Necropsies were conducted at the end of the dosing and recovery phases, and histologic examinations performed. Corneal neovascularization that was considered adverse was observed at doses of >or=1.0 microg/eye and was not reversed by the end of the recovery phase. Dogs dosed with >or=0.25 microg/eye developed a dose-related conjunctival hyperemia that persisted throughout the reversal period. Corneal neovascular cells stained positive with EP4 and the endothelial biomarker Factor VIII-vWF. Other histopathology findings observed at doses of >or=1.0 microg included single-cell necrosis and neutrophils in the cornea, inflammatory cell infiltrates in the iris/ciliary body, and iridal endothelial cell hypertrophy. A resolving acute to subacute inflammation in the iris/ciliary body was observed after the four-week recovery period.
Assuntos
Neovascularização da Córnea/induzido quimicamente , Olho/efeitos dos fármacos , Pirrolidinonas/toxicidade , Receptores de Prostaglandina E/agonistas , Tiofenos/toxicidade , Administração Tópica , Animais , Córnea/efeitos dos fármacos , Córnea/patologia , Cães , Combinação de Medicamentos , Olho/patologia , Fator VIII/análise , Pressão Intraocular/efeitos dos fármacos , Pirrolidinonas/administração & dosagem , Receptores de Prostaglandina E Subtipo EP4 , Tiofenos/administração & dosagem , Testes de Toxicidade , Fator de von Willebrand/análiseRESUMO
OBJECTIVE: PD0325901, a selective inhibitor of mitogen-activated protein kinase kinase (MEK), was associated with the occurrence of ocular retinal vein occlusion (RVO) during clinical trials in patients with solid tumors. As previous animal safety studies in rats and dogs did not identify the eye as a target organ of toxicity, this work was conducted to develop a rabbit model of ocular toxicity with PD0325901. METHODS: Dutch-Belted rabbits were administered a single intravitreal injection of PD0325901 (0.5 or 1 mg/eye) or saline control, and ophthalmic examinations and retinal angiography were conducted over a 2-week period post-dose. In addition, mechanism of ocular toxicity was further explored in rat with microarray analysis. RESULTS: PD0325901 treatment produced RVO with retinal vasculature leakage and hemorrhage within 48-h postinjection in Dutch-Belted rabbits. Subsequent retinal detachment and degeneration were also detected on day 8 postinjection. To evaluate the potential mechanism(s) of PD0325901-mediated RVO, male Brown Norway rats were orally administered PD0325901 (45 mg/kg/day) up to 5 days and retinal tissue was collected for gene array analysis. Although PD0325901 did not produce clinical evidence of RVO in rats, retinal gene expression suggested an increased oxidative stress and inflammatory response, endothelium and blood-retinal barrier damage, and prothrombotic effects. Moreover, soluble endothelial protein C receptor (sEPCR), a biomarker for RVO, was elevated in human umbilical vascular endothelial cells (HUVECs) cultured with PD0325901. CONCLUSIONS: This work has developed a rabbit model of PD0325901-induced RVO that may be used to characterize the cellular and molecular mechanisms of this effect in humans.
Assuntos
Benzamidas/toxicidade , Difenilamina/análogos & derivados , Modelos Animais de Doenças , Inibidores de Proteínas Quinases/toxicidade , Oclusão da Veia Retiniana/induzido quimicamente , Administração Oral , Animais , Antígenos CD/efeitos dos fármacos , Antígenos CD/metabolismo , Benzamidas/administração & dosagem , Células Cultivadas , Difenilamina/administração & dosagem , Difenilamina/toxicidade , Relação Dose-Resposta a Droga , Receptor de Proteína C Endotelial , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/metabolismo , Feminino , Angiofluoresceinografia/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Análise em Microsséries , Quinases de Proteína Quinase Ativadas por Mitógeno/antagonistas & inibidores , Estresse Oxidativo/efeitos dos fármacos , Inibidores de Proteínas Quinases/administração & dosagem , Coelhos , Ratos , Ratos Endogâmicos BN , Receptores de Superfície Celular/efeitos dos fármacos , Receptores de Superfície Celular/metabolismo , Especificidade da Espécie , Veias Umbilicais/citologia , Veias Umbilicais/efeitos dos fármacosRESUMO
Murine cytomegalovirus encodes a secreted, pro-inflammatory chemokine-like protein, MCK-2, that recruits leukocytes and facilitates viral dissemination. We have shown that MCK-2-enhanced recruitment of myelomonocytic leukocytes with an immature phenotype occurs early during infection and is associated with efficient viral dissemination. Expression of MCK-2 drives the mobilization of a population of leukocytes from bone marrow that express myeloid marker Mac-1 (CD11b), intermediate levels of Gr-1 (Ly6 G/C), platelet-endothelial-cell adhesion molecule-1 (PECAM-1, CD31), together with heterogeneous levels of stem-cell antigen-1 (Sca-1, Ly-6 A /E). Recombinant MCK-2 mediates recruitment of this population even in the absence of viral infection. Recruitment of this cell population and viral dissemination via the bloodstream to salivary glands proceeds normally in mice that lack CCR2 and MCP-1 (CCL2), suggesting that recruitment of macrophages is not a requisite component of pathogenesis. Thus, a systemic impact of MCK-2 enhances the normal host response and causes a marked increase in myelomonocytic recruitment with an immature phenotype to initial sites of infection. Mobilization influences levels of virus dissemination via the bloodstream to salivary glands and is dependent on a myelomonocytic cell type other than mature macrophages.